Problem Accessing Obscure Data Variables in Fluent

randomPhil · December 10, 2013, 15:31

hi all,

I'm writing a udf to time average certain variables (for NOx model-LES-combustion) that aren't done normally by Fluent but could really use some help...

Can anyone advise how to retrieve data for obscure variables such as premixed-g-equation, and species concentrations for o2 and n2 using a udf? The problem is that I need to import time-averaged data into the corresponding instantaneous data variables for the NOx post-processing model to use, but the udf manual only has the names for common variables like temperature and mixture fraction

Alternatively can anyone suggest how I may be able to work out the variable names?

Any help is greatly appreciated!!!

macfly · December 11, 2013, 12:27

In the udf manual release 14.5, see Table 3.8: Macros for cell flow variables... You can access species mass fractions with the C_YI(c,t,i) macro.

randomPhil · December 12, 2013, 11:35

hi, thanks for the response!

the problem is that I am using the flamelet model so the code you gave doesn't give the species concentrations as they are mixture fraction quantities instead of being species mass fractions, I was wondering if there is any way to work out the code to use to call the variables not listed in the udf guide?

... I think another similar post suggested writing a data file to see them so possibly this is the solution

macfly · December 12, 2013, 11:42

Still in udf manual release 14.5, section 3.2.3.6.1. says you can retrieve mole/mass fractions into arrays.

December 10, 2013, 15:31	Problem Accessing Obscure Data Variables in Fluent	#1
randomPhil New Member Phil Join Date: Jun 2013 Posts: 11 Rep Power: 12	hi all, I'm writing a udf to time average certain variables (for NOx model-LES-combustion) that aren't done normally by Fluent but could really use some help... Can anyone advise how to retrieve data for obscure variables such as premixed-g-equation, and species concentrations for o2 and n2 using a udf? The problem is that I need to import time-averaged data into the corresponding instantaneous data variables for the NOx post-processing model to use, but the udf manual only has the names for common variables like temperature and mixture fraction Alternatively can anyone suggest how I may be able to work out the variable names? Any help is greatly appreciated!!!

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December 11, 2013, 12:27		#2
macfly Senior Member François Grégoire Join Date: Jan 2010 Location: Canada Posts: 392 Rep Power: 17	In the udf manual release 14.5, see Table 3.8: Macros for cell flow variables... You can access species mass fractions with the C_YI(c,t,i) macro.

December 12, 2013, 11:35		#3
randomPhil New Member Phil Join Date: Jun 2013 Posts: 11 Rep Power: 12	hi, thanks for the response! the problem is that I am using the flamelet model so the code you gave doesn't give the species concentrations as they are mixture fraction quantities instead of being species mass fractions, I was wondering if there is any way to work out the code to use to call the variables not listed in the udf guide? ... I think another similar post suggested writing a data file to see them so possibly this is the solution

December 12, 2013, 11:42		#4
macfly Senior Member François Grégoire Join Date: Jan 2010 Location: Canada Posts: 392 Rep Power: 17	Still in udf manual release 14.5, section 3.2.3.6.1. says you can retrieve mole/mass fractions into arrays.